In this issue:
Upgrading Marine Electrics
Refitting an Open Runabout – Part 2
Technical Brief
Fusing the Negative Circuit of ACRs and Other Electric Relays
Calculating Load Demands for a DC Power Distribution Panel

EVENTS
MAATS 2007 Show
7th annual Marine Aftermarket Accessories Trade Show (MAATS)
Las Vegas Convention Center
July 18-20, 2007

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Look for Blue Sea Systems' booth, number 643. Click here for information about MAATS.


The National Electrical Wire Processing Technology Expo
Midwest Airlines Center, Milwaukee, Wisconsin
May 23-24, 2007

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Look for Blue Sea Systems' booth, number 1549. Click here for information about The National Electrical Wire Processing Technology Expo.


Previous issues of


Issue 37
(April 16, 2007)

Press Release:
Blue Sea Systems' Online DC Circuit Wizard Demystifies Circuit Protection and Wire Sizing

Application Brief:
Introduction to Blue Sea Systems' New Online DC Circuit Wizard

Reference:
Recommended Books on Marine Electrical Systems

Issue 36
(March 15, 2007)

Press Release:
Blue Sea Systems Achieves ISO 9001:2000 Certification

Upgrading Marine Electrics:
Refitting an Open Runabout

Technical Brief:
Preventing Cycling in Battery Combiners, Voltage Sensitive Relays, and Automatic Charging Relays


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Issue 35
(February 16, 2007)

Press Release:
Blue Sea Systems Launches Award-Winning Website

Press Release:
Blue Sea Systems’ ADD A BATTERY is a Complete Two Battery Bank Management System

Technical Brief:
Applications of ACR and Multi-Program Multi-Output Chargers

Technical Brief:
Solving ACR/Multi-Program Multi-Output Charger Interference




For a complete list of past Circuit Solutions™ issues, click here.

Upgrading Marine Electrics
Refitting an Open Runabout – Part 2

Blue Sea Systems took on the refit of the electrical system on a Harborcraft runabout. The refit consisted of adding a second battery, automatic charging relay, battery switch, DC distribution panel, and other improvements. This second Application Brief describes the replacement of the original fuse and switch distribution panel with a Blue Sea Systems WeatherDeck™ Circuit Breaker Panel.

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Click the link below to read the second Application Brief (Part 2).
Application Brief: Refitting With a WeatherDeck™ Circuit Breaker Panel

Click the link below to read the first Application Brief (Part 1).
Application Brief: Adding a Secondary Battery, Battery Switch, and Automatic Charging Relay (ACR)


Technical Brief
- Non-product-specific technical information for improving safety, reliability, and usefulness of marine electrical systems
Fusing the Negative Circuit of ACRs and Other Electric Relays

Automatic charging relays and other electric switches contain a high-amp circuit and a low-amp circuit. A short circuit may occur between the high-amp circuit and low-amp circuit resulting in high current flows through the low-amp circuit. This condition may lead to excessive heating and possible fire. One solution is to add a fuse to the negative wire in the low amp circuit.

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Click the link below to read the Technical Brief.
Technical Brief: Fusing the Negative Circuit of ACRs and other Electric Relays



Calculating Load Demands for a DC Power Distribution Panel

When adding or upgrading a DC power distribution panel, the first step is to determine the current requirements of all loads that will be fed by each circuit in the panel. The current requirement of each load determines the circuit protection rating and the wire size for each branch circuit, and the wire size for the panel feeder wire (both positive feed and negative return).

To calculate load demands for a DC power distribution panel, follow this process:

Inventory all loads, identify them as continuous or intermittent
Calculate total load for panel feed wire—the sum of all continuous loads plus an allowance for intermittent loads
Determine appropriate voltage drop for feeder wire and individual circuit wires
Use Blue Sea Systems’ DC Circuit Wizard to determine:
 - Panel feed wire size
- Circuit protection ratings and wire size for each branch circuit

For a detailed description of this process, see ABYC E11, section 10.1. Many books on marine electrical systems also describe this procedure. For example, Boatowner's Illustated Electrical Handbook by Charlie Wing.

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Copyright ©2007 - Blue Sea Systems, Inc.
425 Sequoia Drive, Bellingham, WA 98226 USA
Phone: 360-738-8230
Fax: 360-734-4195
Website: www.bluesea.com